The invention relates to remote indication or measurement of a condition wherein isolation is required. In many cases a condition is to be remotely indicated where isolation is necessary. For example, the conditions on a high voltage system are to be read at a low voltage location. Alternatively, an inaccessible location is to be monitored remotely for a condition such as temperature, pressure, flow rate, or the like. Typically, isolation is achieved using transformer coupled transducers, amplifiers, or repeaters which must be powered. Also, light beam coupled systems have been used for isolation. Most systems require powered transducer equipment at both the isolated and the measurement sensing locations. Such systems may require separate power supplies and are complicated.